Core barrel valve assembly

ABSTRACT

A valve assembly for use in an inner tube member of a core barrel head assembly positionable within a drill string of a drilling apparatus. The valve assembly works using two separate surfaces A and B and a biasing element with a force F S . When hydrostatic pressure is present forces are created on these surfaces: F A  and F B . These forces have a direct relationship with pressure, as an increase in pressure will increase the force and vice versa. The surface areas are designed such that: F A &gt;F B +F S , which will maintain the valve closed while under a predetermined fluid pressure, indicating to the driller that the inner tube has landed. When the driller relieves the fluid pressure and the pressure decreases, the force difference between F A , F B  and F S  decreases until F A &lt;F B +F S , thus opening the valve for drilling.

FIELD OF THE INVENTION

The present invention generally relates to core barrels. Morespecifically, it relates to a core barrel head assembly.

BACKGROUND OF THE INVENTION

It is known in various connections to use valves that control the supplyof a fluid by being opened when they are subjected to a certain pressurefrom the fluid. One such application is in wire line core drilling, aswill be described below.

When performing exploratory drilling to collect rock samples from depthsof from several hundred to a couple of thousand meters, double coretubes are used having an inner and an outer tube. The sample iscollected in the inner tube, which usually has a length of a few meters.When the inner tube is full this is usually detected by means of amanometer or the like that measures the flushing water pressure in thecore tube. A retriever device suspended on a wire is lowered into thetube for retracting the inner tube with the sample, said retrieverdevice comprising a gripping means in the form of a claw or “spearhead”arranged to engage with a gripping means arranged on/in the upper end ofthe inner tube. When the wire is then tautened the inner tube isdisengaged from the outer tube, and the inner tube with the sample canbe hoisted up. Conversely, the claw and the gripping means on the innertube can be used to lower a new inner tube. Equipment of this type isgenerally known as a wire line system.

When a new inner tube is inserted it is important to be able toascertain that the inner tube really has reached right down to thebottom of the outer tube and has assumed its correct position fordrilling, before drilling is commenced. Ascertainment that the tube canno longer move, but is firmly held is generally taken as an indicationthat the inner tube has reached its correct position. According to knowntechnology, therefore, the gripping means is often designed to becombined with some type of locking member that firmly locks the innertube in relation to the outer tube when the inner tube has reached thecorrect position. This locking member usually consists of a hook-likedevice, preferably spring-loaded, a locking claw or latch that engageswith recesses or shoulders arranged in the inside of the outer tube.Actual insertion of the inner tube is usually performed by the innertube being “pumped” along inside the drill string with the aid of water.When the inner tube is firmly in place the water pressure will increaseto such an extent that a valve arranged for flushing medium in the innertube is released.

One problem with such known arrangements is that when the inner tube isinserted into the drill string it sometimes catches before it hasreached the correct position for drilling. With designs currently inuse, the increase in water pressure then occurring will release theflushing valve before the inner tube has reached its correct positionand, in the worst case, drilling will be commenced. This primarilyentails a disadvantage from the financial point of view since thedrilling will be into thin air. There is also a risk of the core at thebottom being destroyed. Hence it is useful to provide a landingindicator system in order to ensure that the inner tube has reached itscorrect position.

The current industry standard to provide a landing indicator system usesa ball and bushing or plunger (ball attached to retracting case) andbushing as a valve assembly with short signal duration.

The current standard for a core barrel valves has a pressure signal thatis very short in duration and can be easily missed by the driller and isnot reliable on deeper holes and requires frequent replacement.Previously known valves with sustained pressure signals were notreliable due to mud and debris jamming the moving parts of the valve.Previous valves also were limited in hole conditions with a very lowwater table and very deep holes, as they could not cope with the largedifferences in hydrostatic pressure.

The system described in U.S. Pat. No. 6,708,784 attempted to remedy someof the above-described problems. U.S. Pat. No. 6,708,784 disclosesmethod for a valve, the valve comprising a movable valve element havinga first side facing a means for supplying pressurized fluid andinfluenced in the supply direction by a force from said fluid, and asecond side influenced in opposite direction by a force from said fluid.The valve is provided with at least one connection connecting the firstside of the valve element with the second side of the valve element, andalso comprises a spring for opening the valve by displacing the valveelement from a closed position to an open position. The method comprisesthe following steps: a pressurized fluid is supplied to the valve in theclosed position so that the valve remains closed; the supply ofpressurised fluid to the closed valve ceases, a pressure forcedifferential then decreases between the first and second sides therebyenabling the spring to open the valve, and a pressurized fluid issupplied to the valve in the open position and the valve remains open.

However, the valve assembly described in U.S. Pat. No. 6,708,784 is notself-resetting and does not function properly when debris and/oradditives are present in the flushing medium.

Consequently, there is still presently a need for a valve assembly for alanding indicator system that is self-resetting and that will work withdebris and/or additives in the flushing medium, while functioningproperly in low water level conditions and in shallow holes.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a valve assemblythat addresses at least one of the above-mentioned needs.

Accordingly, the present invention provides a valve assembly for use ina core barrel head assembly positionable within a drill string of adrilling apparatus, the valve assembly comprising:

-   -   a landing shoulder;    -   at least one upstream fluid flow port positionable within a        fluid line of the drilling apparatus upstream of the landing        shoulder;    -   at least one downstream fluid flow port positionable within the        fluid line of the drilling apparatus downstream of the landing        shoulder;    -   at least one fluid pressure communication port positionable        within the fluid line of the drilling apparatus;    -   a movable valve element having a first side in fluid        communication with pressurized fluid through the at least one        pressure port and having a first surface that is influenced in        the supply direction by a force F_(A) from said fluid, and a        second side facing in the opposite direction, in fluid        communication with pressurized fluid through the at least one        upstream fluid flow port and having a second surface that is        influenced in the opposite direction by a force F_(B) from said        fluid;    -   at least one biasing element for opening the valve assembly by        displacing the valve element from a closed position to an open        position,        wherein the area of said second surface is greater than that of        said first surface so that the force influencing the valve        element in a closing direction, in the form of the force F_(B)        from the pressurized fluid acting on said second surface exceeds        the force influencing the valve element in an opening direction,        in the form of the combined force Fs from the biasing element        and the force F_(A) from the pressurized fluid acting on said        first surface, whereby the valve element is retained in the        closed position of the valve when pressurized fluid is supplied.

According to the present invention, there is also provided a method foroperating a valve assembly for use in a core barrel head assemblypositionable within a drill string of a drilling apparatus driven bypressurized fluid, the valve assembly comprising:

-   -   a landing shoulder;    -   at least one upstream fluid flow port positionable within a        fluid line of the drilling apparatus upstream of the landing        shoulder;    -   at least one downstream fluid flow port positionable within the        fluid line of the drilling apparatus downstream of the landing        shoulder;    -   at least one fluid pressure communication port positionable        within the fluid line of the drilling apparatus;    -   a movable valve element having a first side in fluid        communication with pressurized fluid through the at least one        pressure port and having a first surface that is influenced in        the supply direction by a force F_(A) from said fluid, and a        second side facing in the opposite direction, in fluid        communication with pressurized fluid through the at least one        upstream fluid flow port and having a second surface that is        influenced in the opposite direction by a force F_(B) from said        fluid;    -   at least one biasing element for opening the valve assembly by        displacing the valve element from a closed position to an open        position,    -   wherein the area of said second surface is greater than that of        said first surface so that the force influencing the valve        element in a closing direction, in the form of the force F_(B)        from the pressurized fluid acting on said second surface exceeds        the force influencing the valve element in an opening direction,        in the form of the combined force Fs from the biasing element        and the force F_(A) from the pressurized fluid acting on said        first surface,        the method comprising the steps of:    -   a) supplying the pressurized fluid to the valve element in its        closed position whereupon the valve assembly remains closed;    -   b) reducing the supply of pressurized fluid to the closed valve        assembly; and    -   c) allowing a pressure force differential to decrease between        said first and second sides, thereby enabling the biasing        element to urge the valve element towards the open position, and        thereby allowing fluid flow through the at least one upstream        fluid flow port.

In accordance with the present invention, there is also provided wireline core drill system comprising a wire line core drill having an innertube by means of which core samples are collected, an outer tubeconnected to a drill bit, and a valve assembly situated at the rear endof the inner tube, the valve assembly controlling the supply of aflushing medium in the form of a pressurized fluid, wherein the valveassembly is constructed as described above.

The valve assembly according to the present invention provides twoseparate ports upstream of the landing shoulder and allowing fluidpressure to apply a force on two different surfaces eliminating smallfluid passages that are prone to blockage from debris and allowing forsignificantly less restricted flow for drilling when the valve is open.Fluid pressure can be required to lock the latches engaged in the drillstring. This ensures that the valve assembly will remain closed when thehead has landed but fluid pressure has not yet built up. This featurealso greatly decreases the pressure applied by the latches to the insidewall of the drill string while it is travelling down the drill string,greatly reducing the friction, decreasing wear on the latches anddecreasing the time to travel to the bottom of the hole. The valveassembly can thus function in low water level conditions and in shallowholes.

The valve assembly according to certain embodiments of the presentinvention can also be self-resetting, a feature not present in thesystem described in U.S. Pat. No. 6,708,784. The system described inU.S. Pat. No. 6,705,784 would also not function properly when debris waspresent between sliding surfaces of the valves. However, the valveassembly according to the present also provides a reduced slidingsurface area with seals added to block debris from entering these areas.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the detailed description of thepreferred embodiments of the present invention, will be betterunderstood when read in conjunction with the appended drawings. For thepurpose of illustrating the invention, there is shown in the drawings,which are diagrammatic, embodiments that are presently preferred. Itshould be understood, however, that the present invention is not limitedto the precise arrangements and instrumentalities shown. In thedrawings:

FIG. 1 is an exploded view of a head assembly according to a preferredembodiment of the present invention, with interchangeable mid latchbodies.

FIGS. 2A to 2C are cross-sectional side views of a head assemblyaccording to another preferred embodiment of the present invention.

FIGS. 3A to 3C are detailed cross-sectional side views of the headassembly corresponding to the views shown in FIGS. 6A to 6C,illustrating flow streamlines through the valve assembly.

FIGS. 4A to 4D are partial detailed cross-sectional side views of thehead assembly with a valve assembly according to another preferredembodiment of the present invention, illustrating a preferred sequentialuse of the valve assembly.

FIGS. 5A and 5B are partial side views of an upper latch body and latchretracting case of the head assembly shown in FIGS. 6A to 6C.

FIGS. 6A and 6B are a partial cross-sectional view of a valve assemblyand partial side view of a joined upper latch body and latch retractingcase, respectively, of the head assembly shown in FIGS. 6A to 6C, duringa descent phase of a preferred sequential use of the valve assembly.

FIGS. 7A and 7B are a partial cross-sectional view of a valve assemblyand partial side view of a joined upper latch body and latch retractingcase, respectively, of the head assembly shown in FIGS. 6A to 6C, duringa signal phase of a preferred sequential use of the valve assembly.

FIGS. 8A and 8B are a partial cross-sectional view of a valve assemblyand partial side view of a joined upper latch body and latch retractingcase, respectively, of the head assembly shown in FIGS. 6A to 6C, duringa working phase of a preferred sequential use of the valve assembly.

FIGS. 9A and 9B are a partial cross-sectional view of a valve assemblyand partial side view of a joined upper latch body and latch retractingcase, respectively, of the head assembly shown in FIGS. 6A to 6C, duringa transition to the retracting/retrieval phase of a preferred sequentialuse of the valve assembly.

FIGS. 10A and 10B are a partial cross-sectional view of a valve assemblyand partial side view of a joined upper latch body and latch retractingcase, respectively, of the head assembly shown in FIGS. 6A to 6C, duringa retracting/retrieval phase of a preferred sequential use of the valveassembly.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “mounted,” “connected,” “supported,” and “coupled” and variationsthereof are used broadly and encompass both direct and indirectmountings, connections, supports, and couplings and are thus intended toinclude direct connections between two members without any other membersinterposed therebetween and indirect connections between members inwhich one or more other members are interposed therebetween. Further,“connected” and “coupled” are not restricted to physical or mechanicalconnections or couplings. Additionally, the words “lower”, “upper”,“upward”, “down” and “downward” designate directions in the drawings towhich reference is made. The terminology includes the words specificallymentioned above, derivatives thereof, and words or similar import.

Referring now to the drawings in detail, wherein like numbers are usedto indicate like elements throughout, there is shown in FIG. 1 anexploded view of a presently preferred embodiment of an core barrel headassembly 10 for a drilling apparatus.

The core barrel head assembly 10 is positionable within a drill stringof a drilling apparatus. The core barrel head assembly 10 comprises anupper latch body 12 and a lower latch body 14. The head assembly 10further comprises a mid latch body 16 separating the upper latch body 12from the lower latch body 14 and removably coupling the upper latch body12 to the lower latch body 14. FIG. 1 shows three different sampleembodiments of the mid latch body 16A, 16B, 16C to illustrate theinterchangeability of the mid latch body 16. In all cases, the mid latchbody 16 is removably coupled to the upper latch body 12 and the lowerlatch body 14. The mid latch body 16 houses a landing indicator device18. A common central bore 20 is formed by the upper latch body 12, thelower latch body 14 and the mid latch body 16.

Preferably, as illustrated in FIG. 1, the head assembly includes anupper latch body 12 with a latching assembly 30 and fluid pressurecommunication ports 32. The lower latch body 14 holds a landing shoulder34 by a removable sleeve 36 and includes fluid flow ports 38 downstreamof the landing shoulder. The mid latch body component 16 also has fluidflow ports 40 upstream of the landing shoulder, and connects the upperand lower latch bodies, 12,14, with a central bore 20 connecting thefluid flow ports 38,40. The mid latch body 16 contains a valvingmechanism 42 which can provide a landing indication signal. The commoncentral bore 20 is present through all body components. The headassembly preferably includes of two sets of ports: the first set forfluid pressure communication with the internal valving mechanism 42, thesecond set for fluid flow required for drilling in which the fluid flowis blocked or opened by the internal valving mechanism 42. This fluidport design offers the advantages of increased fluid flow duringdrilling which means it is less likely to collect debris and pack withmud and thus results also in a more efficient pumping system, comparedto a head assembly where all the fluid circulates through a single portsystem upstream of the landing shoulder (thus more subject to blockage)from the upper latch body to the lower latch body, with no bypass port.Given the reconfigurable nature of the head assembly, different valvingsystems can be used depending on drilling conditions and also can beeasily upgraded when a newer type of valve is developed. FIG. 1illustrates an example of three different head assemblies in which theupper 12 and lower 14 latch bodies are similar and could be shared, butwhere a changeout of the mid latch body 16 allows the use of differentvalving mechanism designs that can be tailored to a specific drillingcondition.

The following sections will illustrate different valving mechanisms thatcan be changed out through different mid latch bodies 16 while alsobenefiting from the advantages of having the distinct fluid pressurecommunication ports 32 and fluid flow ports 40 upstream of the landingshoulder.

Fluid Controlled Valves

FIG. 2A-10B show different embodiments of a head assembly in accordancewith another preferred embodiment of the present invention. Once again,the head assembly allows for an interchangeable mid latch body 16between an upper latch body 12 and a lower latch body 14. Also, thevalving assembly in the mid latch body benefits from the use of separatepressure communication ports 32 and fluid flow ports 40. The headassembly includes a valve assembly 100 for use in a core barrel headassembly 10 positionable within a drill string of a drilling apparatus.The valve assembly 100 comprises at least one pressure port 32 formed ina sidewall of the core barrel head assembly 100 upstream of the landingshoulder. There is also at least one fluid flow port 40 formed in thesidewall of the core barrel head assembly 100 upstream of the landingshoulder. The valve assembly 100 also includes a movable valve element218 having a first side 220 in fluid communication with pressurizedfluid through the head assembly and having a first surface that isinfluenced in the supply direction by a force F_(A) from said fluid. Asecond side 222 faces in the opposite direction, in fluid communicationwith the pressurized fluid through the head assembly and having a secondsurface that is influenced in the opposite direction by a force F_(B)from the fluid. A biasing element, such as a spring 224 or anyequivalent resilient element is provided for urging the valve assemblytowards an opened configuration by displacing the valve element 218 froma closed position, blocking the at least one fluid flow port 40, to anopen position. The biasing element or spring may be designed to beadjustable

The area of the second surface is greater than that of the first surfaceso that the force influencing the valve element 218 in a closingdirection, in the form of the force F_(B) from the pressurized fluidacting on the second surface exceeds the force influencing the valveelement in an opening direction, in the form of the combined force Fsfrom the spring and the force F_(A) from the pressurized fluid acting onthe first surface, whereby the valve element is retained in the closedposition of the valve when pressurized fluid is supplied, as illustratedin FIGS. 2A and 3A

Preferably, upon a reduction in the supply of pressurized fluid to theclosed valve, the pressure force differential decreases between saidfirst and second sides 220,222, and the spring 224 then urges the valveelement 218 to be displaced from its closed position to its openposition unblocking the at least one fluid flow port 40 as shown inFIGS. 2B and 3B.

Preferably, the valve assembly further comprises a locking device formechanically locking the valve element in its closed position. In onepossible embodiment illustrated in FIG. 4A to 4D, the locking devicecomprises a pressure sleeve 226 mechanically connected through theretracting case 28 to a latch locking mechanism 232 of the inner tubemember. Another possible embodiment of the locking device is illustratedin FIG. 2A to 3C and FIG. 5A-10B and will be described in further detailbelow.

According to the present invention, there is also provided a method foroperating the valve assembly for use in a core barrel head assemblypositionable within a drill string of a drilling apparatus driven bypressurized fluid, the method comprising the steps of:

-   -   a) supplying the pressurized fluid to the valve element 218 in        its closed position whereupon the valve assembly remains closed;    -   b) reducing the supply of pressurized fluid to the closed valve        assembly; and    -   c) allowing a pressure force differential to decrease between        the first and second sides 220,222, thereby enabling the biasing        means 224 to urge the valve element 18 towards the open        position, and thereby allowing fluid flow through the at least        one fluid flow port and remain open.

Preferably, when the valve assembly 100 further comprises a lockingdevice for mechanically locking the valve element in its closedposition, in step a), the valve element is in a mechanically lockedclosed position, and the method further comprises the step, betweensteps a) and b) of:

-   -   i) causing the locking device to cease locking the valve element        218 in the closed position.

Preferably, the locking device comprises a pressure sleeve 226mechanically connected to a latch locking mechanism 232 of the headassembly and step i) further comprises the step of allowing fluidpressure to displace the pressure sleeve 226 and engage a latch lock 228of the latch locking mechanism 232.

As mentioned above, another embodiment of the fluid controlled valveassembly, and in particular the locking device, illustrated in FIG.2A-3C and 5A-10B, will now be presented. Preferably, the valve elementis a two-piece valve comprising a valve body 250 and a valve piston 252.The valve body 250 is used to selectively block the fluid flow port 40and includes a side 222 which applies a force to urge the valve assemblytowards a closed configuration. The valve piston 252 includes a side 220which applies a force to urge the valve assembly towards an openconfiguration, The valve piston 252 further comprises a slotted stem 254to allow fluid flow to flush debris and a pin 256 to co-operate with theprofiled slots in the upper latch body 12 and latch retracting case 28to be able to selectively lock the valve assembly in a closedconfiguration.

Preferably, as better shown in FIG. 5A the upper latch body 12 comprisesa profiled slot 258 to co-operate with the pin 256 of the valve piston252 to lock the valve-in the closed position and allow the valve to moveto the open position after a predetermined rise in fluid pressure. Morespecifically, the profiled slot 258 allows axial movement of the pinwithin the main slot portion 260. A top end 262 of the slot 258 extendsat an angle transversely with respect to the main slot portion, at leastpartially radially and towards the opposite bottom end to prevent thepin 256 from moving downward. The pin 256 is held in the radiallyextended slot position by the spring 224 that biases the valve assemblytowards the open position.

Preferably, as the fluid pressure rises and the force on the surface ofside 220 overcomes the spring force, both valve body 250 and piston 252will move up and the pin 256 on the valve piston 252 will be directed bythe angled slot extension 262 to move the pin 256 radially (or rotateit) towards the main slot portion 260 to allow for axial movement of thepin and hence the valve member when the pressure is released.

Preferably, as shown in FIG. 5B, the latch retracting case 28 also has aprofiled slot 270 to cooperate with the pin 256 on the valve piston 252.The latch retracting case 28 automatically moves the pin 256 to thelocked position on the profiled slot 258 of the upper latch body 12 whenthe latches 142 are retracted. The profiled slot thus helps to hold thelatch retracting case 28 and latch lock in an intermediate up positionsuch that the latch lock is not engaged to the latches 142, greatlyreducing the latch drag on the drill rod during descent.

The profiled slot 270 allows for axial movement of the pin 256 within amain slot portion 272. A bottom end 274 of the slot extends at an anglewith respect to the main slot portion 272, at least partially radiallyand axially lower than the main slot portion 272, thus rotating the pin256 towards the locked position in the upper latch body 12 when thelatch retracting case 28 is moved up to retract the latches 142. The pin256 during the latch retraction can then extend back towards the bottomend 274 in a direction parallel to the main slot.

Preferably, when released from the overshot and during descent, thebiasing means 280, such as a spring or other equivalent resilientelement, in the retracting case 28 will bias the retracting case 28towards the down position. The bottom end portion 274 of the profiledslot 270 will prevent the retracting case 28 from moving to the fullydown position as it is being held in an intermediate up position,preventing the latch lock from engaging with the latches 142, once againgreatly reducing the latch drag on the drill rod during descent.

An operational sequence of the valve assembly will now be described.Reference will be made to components illustrated in the two differentgroups of embodiments illustrated respectively in FIG. 2A to 3C/5A to10B and FIG. 4A to 4D.

Descent

Before inserting the inner tube head assembly in the drill string, thelatch retracting case 28 is pulled up (right side in FIG. 2A, 4A or 6A)to its first position. This will disengage the latch lock 228 and allowthe latches 142 to move freely from the engaged position to theretracted position and vice versa. The valve biasing means 224 andretracting case biasing means 236 are compressed. In the embodimentshown in FIG. 4A, the latch retracing case 28 is directly connected tothe pressure sleeve 226. The pressure sleeve 226 and/or the latchretracting case 28 are held in this first position (with a mechanicallock) as it is travelling through the drill string, to reduce the latchdrag on the drill rod during descent. In the embodiment shown in FIG. 2Aor 6A-6B, the pin 256 attached to the valve piston 252 is constrainedthrough interaction with profiled slots 258, 270 and thus prevented frommoving down to lock the latches 142, thereby reducing latch drag on thedrill rod. The valve body 250 blocks fluid flow through the fluid flowport 40.

Signal

When the head assembly 10 has landed in the correct position, for theembodiment shown in FIG. 4B, fluid pressure will increase and act on thesurface 220 and push with a force at a first predetermined value lessthan a second predetermined value, such as for example, maximum pumppressure, to move the pressure sleeve 226 down and engage the latch lock228 with which it is directly connected through the latch retractingcase 28. In this configuration, the latches 142 are engaged and lockedinto the outer tube and the valve element 218, which is connected to theretracting case 28 by slot 242 is allowed to operate normally. If thelatches 142 are not in the correct position, the latch lock 228 and itsdirectly connected components will not be able to move down to thesecond position and allow the valve to operate normally. Fluid pressurewill remain high even after it has been released to the atmosphere,indicating to the driller that the latches are not properly engaged andcorrective action must be taken. In the second position, the fluidpressure continues to rise and acts on first surface 220 throughpressure communication port 32 and second surface 222 through fluid flowport 38. The first surface area is smaller than the second surface areasuch that when fluid pressure is present, the force generated by thesecond surface area is greater than the combined force generated by thefirst surface area and the force of the spring 224. This will maintainthe valve in the closed position while fluid pressure is acting on thevalve.

For the embodiment shown in FIG. 7A-7B, under similar fluid pressureconditions, the increased pressure will displace the valve body 250 andvalve piston 252 up, which through interaction with the profiled slots258,260, induces rotation of the pin 256 out of its lockedconfiguration. This permits the valve piston 252 to move and allows theretracting case 28 to descend while the latches 142 become engaged.However, if the latches 142 are jammed, the retracting case 28 will notmove down, thus blocking movement of the valve 252 piston and valveassembly and preventing opening of the fluid flow port 40.

Working

For the embodiment shown in FIG. 4C, when the fluid pump is stopped andthe pressure is relieved, a pressure force differential decreasesbetween the first and second surfaces 220,222 so that the biasing means224 or spring force will move the valve element 218 down to an open,third position. The pump will then be turned back on and drilling fluidwill flow freely through fluid flow port 40 to the drill bit fordrilling.

For the embodiment shown in FIGS. 2B and 8A, 8B, once fluid pressure isrelieved, the biasing means 224 or spring force also overcomes thepressure force differential between the first and second surfaces220,222 to urge the valve element 218 towards an open position. In thisconfiguration, fluid flows through the slots in the valve piston 254 andthrough the valve body 250 into the central bore 20.

Retracting/Retrieval

When the inner tube is full of core, the retrieval device or overshot issent down the drill string and connects to the spearhead 50. For theembodiment shown in FIG. 4D, the spearhead 50, which is connected to theretracting case 28 is pulled up for retrieval and moves the retractingcase 28 up past the first position it had during descent to its fourthposition. The valve element 218 and valve body 250, being slideablyconnected to the retracting case 28, is moved up past the first positionas well to allow fluid to flow through the apertures 260. When theovershot is disconnected from the spearhead 50, the spring 236 willreturn the valve assembly to the first descent position and it will beready for the next trip down the hole.

For the embodiment shown in FIGS. 2C and 9A-9B, under similarconditions, retraction of the retracting case 28, induces rotation ofthe pin 256 towards a locked configuration thus keeping the latches 142in an unlatched configuration and minimize drag of the latches on thedrill rod during retrieval of the spearhead 50. This configuration alsopositions the valve body 250 in a configuration which keeps the fluidflow port 40 open during the retrieval operation.

Reset

For the embodiment shown in FIG. 10A-10B, once the valve assembly isreturned to the surface, the valve body 150 must be displaced manuallyat the surface location in order to position the valve body 150 in aclosed configuration that will be ready once again for the next descentdown the hole. For the embodiment shown in FIGS. 4A-4D, the reset can bedone automatically.

The present invention also provides a wire line core drill systemcomprising a wire line core drill having an inner tube by means of whichcore samples are collected, an outer tube connected to a drill bit, anda valve assembly situated at the rear end of the inner tube, said valveassembly controlling the supply of a flushing medium in the form of apressurized fluid, wherein the valve assembly is constructed asdescribed in one of the embodiments provided above.

Although preferred embodiments of the present invention have beendescribed in detail herein and illustrated in the accompanying drawing,it is to be understood that the invention is not limited to theseprecise embodiments and that various changes and modifications may beeffected therein without departing from the scope of the presentinvention.

1. A valve assembly for use in a core barrel head assembly positionablewithin a drill string of a drilling apparatus, the valve assemblycomprising: a landing shoulder; at least one upstream fluid flow portpositionable within a fluid line of the drilling apparatus upstream ofthe landing shoulder; at least one downstream fluid flow portpositionable within the fluid line of the drilling apparatus downstreamof the landing shoulder; at least one fluid pressure communication portpositionable within the fluid line of the drilling apparatus; a movablevalve element having a first side in fluid communication withpressurized fluid through the at least one pressure communication portand having a first surface that is influenced in the supply direction bya force F_(A) from said fluid, and a second side facing in the oppositedirection, in fluid communication with pressurized fluid through the atleast one upstream fluid flow port and having a second surface that isinfluenced in the opposite direction by a force F_(B) from said fluid;at least one biasing element for opening the valve assembly bydisplacing the valve element from a closed position to an open position,wherein the area of said second surface is greater than that of saidfirst surface so that the force influencing the valve element in aclosing direction, in the form of the force F_(B) from the pressurizedfluid acting on said second surface exceeds the force influencing thevalve element in an opening direction, in a form of combining a force Fsfrom the biasing element and the force F_(A) from the pressurized fluidacting on said first surface, whereby the valve element is retained inthe closed position of the valve when pressurized fluid is supplied andwherein the at least one fluid pressure communication port and the atleast one upstream fluid flow port form two sets of ports, the first setfor fluid pressure communication with the movable valve element, and thesecond set for fluid flow required for drilling in which the fluid flowis blocked or opened by the movable valve element.
 2. The valve assemblyaccording to claim 1, wherein, upon a reduction in the supply ofpressurized fluid to the closed valve, a pressure force differentialdecreases between said first and second sides, and the biasing elementthen urges the valve element to be displaced from said closed positionto said open position.
 3. The valve assembly according to claim 1,further comprising: a locking device for mechanically locking the valveelement in its closed position.
 4. The valve assembly according to claim3, wherein the locking device comprises a pressure sleeve mechanicallyconnected to a latch locking mechanism of the inner tube member.
 5. Thevalve assembly according to claim 3, wherein the valve elementcomprises: a valve body comprising the second surface; and a valvepiston comprising: a piston element comprising the first surface; aslotted stem linking the piston element to the valve body; and a pinattached to piston element and projecting radially away from the pistonelement, and wherein the locking device comprises: an upper latch bodyhaving a first profiled slot cooperating with the pin, said first slotcomprising a main portion extending along an axial direction and asecondary portion extending in a direction transverse and radial to saidaxial direction; and a latch retracting case coaxially displaceable withrespect to the upper latch body and overlapping over the upper latchbody, the latch retracting case having a second profiled slotcooperating with the pin, said second slot comprising a main portionextending along the axial direction and a secondary portion extending ina direction transverse to said axial direction, parallel to thetransverse direction in which the secondary portion of the first slotextends, said latch retracting case cooperating with a latch lockingmechanism of the inner tube member, such that the valve element islocked and the latch retracting case prevents the latch lockingmechanism from engaging with latches of the core barrel head assemblyupon displacement of the pin in the secondary portions of the first andsecond profiled slots.
 6. A method for operating a valve assembly foruse in a core barrel head assembly positionable within a drill string ofa drilling apparatus driven by pressurized fluid, the valve assemblycomprising: a landing shoulder; at least one upstream fluid flow portpositionable within a fluid line of the drilling apparatus upstream ofthe landing shoulder; at least one downstream fluid flow portpositionable within the fluid line of the drilling apparatus downstreamof the landing shoulder; at least one fluid pressure communication portpositionable within the fluid line of the drilling apparatus; a movablevalve element having a first side in fluid communication withpressurized fluid through the at least one pressure port and having afirst surface that is influenced in the supply direction by a forceF_(A) from said fluid, and a second side facing in the oppositedirection, in fluid communication with pressurized fluid through the atleast one upstream fluid flow port and having a second surface that isinfluenced in the opposite direction by a force F_(B) from said fluid;at least one biasing element for opening the valve assembly bydisplacing the valve element from a closed position to an open position,wherein the area of said second surface is greater than that of saidfirst surface so that the force influencing the valve element in aclosing direction, in the form of the force F_(B) from the pressurizedfluid acting on said second surface exceeds the force influencing thevalve element in an opening direction, in a form of combining a force Fsfrom the biasing element and the force F_(A) from the pressurized fluidacting on said first surface and wherein the at least one fluid pressurecommunication port and the at least one upstream fluid flow port formtwo sets of ports, the first set for fluid pressure communication withthe movable valve element, and the second set for fluid flow requiredfor drilling in which the fluid flow is blocked or opened by the movablevalve element, the method comprising: supplying the pressurized fluid tothe valve element in said closed position whereupon the valve assemblyremains closed; reducing the supply of pressurized fluid to the closedvalve assembly; and allowing a pressure force differential to decreasebetween said first and second sides, thereby enabling the biasingelement to urge the valve element towards the open position, and therebyallowing fluid flow through the at least one upstream fluid flow port.7. The method according to claim 6, wherein the valve assembly furthercomprises a locking device for mechanically locking the valve element insaid closed position, wherein during supplying the pressurized fluid thevalve element is in a mechanically locked closed position, the methodfurther comprising: causing the locking device to cease locking thevalve element in the closed position after supplying the pressurizedfluid and before reducing the supply of pressurized fluid.
 8. The methodaccording to claim 7, wherein the locking device comprises a pressuresleeve mechanically connected to a latch locking mechanism of the innertube member and supplying pressurized fluid further comprises allowingfluid pressure to displace the pressure sleeve and engage a latch lockof the latch locking mechanism.
 9. The method according to claim 7,wherein the valve element comprises: a valve body comprising the secondsurface; and a valve piston comprising: a piston element comprising thefirst surface; a slotted stem linking the piston element to the valvebody; and a pin attached to piston element and projecting radially awayfrom the piston element, wherein the locking device comprises: an upperlatch body having a first profiled slot cooperating with the pin, saidfirst slot comprising a main portion extending along an axial directionand a secondary portion extending in a direction transverse and radialto said axial direction; and a latch retracting case coaxiallydisplaceable with respect to the upper latch body and overlapping overthe upper latch body, the latch retracting case having a second profiledslot cooperating with the pin, said second slot comprising a mainportion extending along the axial direction and a secondary portionextending in a direction transverse to said axial direction, parallel tothe transverse direction in which the secondary portion of the firstslot extends, said latch retracting case cooperating with a latchlocking mechanism of the inner tube member, such that the valve elementis locked and the latch retracting case prevents the latch lockingmechanism from engaging with latches of the core barrel head assemblyupon displacement of the pin in the secondary portions of the first andsecond profiled slots, and wherein supplying pressurized fluid furthercomprises displacing the pin from the secondary portions to the mainportions of the first and second profiled slots, upon proper deploymentof the latch locking mechanism, thereby allowing axial movement of thepin and valve piston.
 10. A wire line core drill system, comprising: awire line core drill having an inner tube configured to collect coresamples, an outer tube connected to a drill bit, and a valve assemblysituated at the rear end of the inner tube, said valve assemblycontrolling the supply of a flushing medium in the form of a pressurizedfluid, wherein the valve assembly comprises a landing shoulder, at leastone upstream fluid flow port positionable within a fluid line of thedrilling apparatus upstream of the landing shoulder, at least onedownstream fluid flow port positionable within the fluid line of thedrilling apparatus downstream of the landing shoulder, at least onefluid pressure communication port positionable within the fluid line ofthe drilling apparatus, a movable valve element having a first side influid communication with pressurized fluid through the at least onepressure communication port and having a first surface that isinfluenced in the supply direction by a force F_(A) from said fluid, anda second side facing in the opposite direction, in fluid communicationwith pressurized fluid through the at least one upstream fluid flow portand having a second surface that is influenced in the opposite directionby a force F_(B) from said fluid, and at least one biasing element foropening the valve assembly by displacing the valve element from a closedposition to an open position, wherein the area of said second surface isgreater than that of said first surface so that the force influencingthe valve element in a closing direction, in the form of the force F_(B)from the pressurized fluid acting on said second surface exceeds theforce influencing the valve element in an opening direction, in a formof combining a force Fs from the biasing element and the force F_(A)from the pressurized fluid actin on said first surface, whereby thevalve element is retained in the closed position of the valve whenpressurized fluid is supplied and wherein the at least one fluidpressure communication port and the at least one upstream fluid flowport form two sets of ports, the first set for fluid pressurecommunication with the movable valve element, and the second set forfluid flow required for drilling in which the fluid flow is blocked oropened by the movable valve element.